The present invention relates to a method for producing fibrous products. More particularly, the present invention relates to a method whereby a superheated zone is utilized to promote bubbling of an aqueous binder solution, added to a fiber felt prior to drying, thus reducing the quantity of binder materials required to manufacture or improve the quality of the fibrous products.
The invention also relates to the combination of a superheated zone and a pretreatment of a certain percentage of the cellulosic wood pulp with a weak alkali containing water and a treatment of another percentage of the cellulosic wood pulp with a weak acid containing water to transform the surfaces of the fibers so as to obtain two different sorts of surfaces of the cellulosic wood fibers--seemingly unchanged--however, adhering to become unified under pressure, heat and moisture.
According to the invention the above mentioned alteration of cellulosic wood fibers, combined with the use of the superheated zone and combined with embossing, calendering or creping to produce a fibrous product, makes conventional pre-beating of wood cellulosic fibers superfluous for many products, since this strength-weakening beating becomes surprisingly unnecessary for many products.
The invention also concerns a fibrous product, produced in accordance with the invention, where the surfaces of two different quantities of cellulosic wood fibers are turned into invisibly "alkalinized" respective --acetated" fibers thus creating--in the fibrous end product--a two-component Ph-neutral bond.
The term cellulosic fibrous products comprises products such as wipers, kitchen paper, writing paper and toilet paper, diapers, table cloth, napkins, tissues, facial-tissues and various other products ranging from 30 grams to more than 200 grams per square meter.
During the last decades, the method of air-forming of fibers to produce paper products and non-wovens, facial tissues, toilet paper etc. etc. was developed.
one of the so-called Kroyer-Methods is especially explained in U.S. Pat. No. 4,494,278 (combined fiber distributors). The Kroyer-Methods also comprise the use of hammermills together the Drum Formers which have a perforated rounded bottom and some inside moving parts (Kroyer Know-How and a.o. Canadian Patent No. 868,142).
The Air-Forming Method solves not only pollution problems and saves energy, it also makes it possible to produce soft and absorbent products and non-wovens having a more textile-like character than usual.
The Air-Forming Method is not limited to soft products such as tissues and non-wovens. Also products which are much more stiff in character, such as packaging material, different sorts of board and any of various high-pressure laminated plastic sheets of melamine and phenolic materials known as FORMICA.RTM., have been made industrially.
Many products, after they have been air-formed, are sprayed with an emulsion, which is often a latex emulsion, used as a binder material. It is not unusual that the emulsion to be added to the fiber felt contains 10% by weight to 20% by weight of the dried substance in the end product.
Accordingly, it would be desirable to produce fibrous products such as those described above with acceptable strength but requiring a much smaller quantity of binder material.
The problems referred to above are not exhaustive but are among those which reduce the number of advantages of the prior methods of producing fibrous products.
Other noteworthy problems may also exist, however, those presented above should be sufficient to demonstrate that fibrous product methods, here in the prior art, have not been altogether satisfactory as regards quality. Products with such a high content of binder as from 10% to 20% dry substance (which is much more expensive than cellulosic wood fibers) are unnecessarily costly to produce.